Reliability of an all-optical differential current detection technique during environmental temperature perturbations

The reliability of a novel, all-optical differential current protection scheme over varying environmental conditions is investigated in this paper. By monitoring the optical power reflected from two matched hybrid fiber Bragg grating current sensors and using a simple and low-cost optoelectronic threshold detector, a sub-cycle response to an increase in differential current can be achieved. A preliminary laboratory embodiment is constructed in order to emulate a practical deployment of the sensors and characterize the performance of the scheme when the sensors are at different temperatures. We demonstrate that even at a temperature difference of 20 °C between the sensors the system is capable of robust and fast-acting fault detection.

I. Introduction

Differential unit protection is widely used in both terrestrial and marine power systems for transmission lines, transformers, tapped lines, motors, generators or busbars protection. It relies on the measurement and comparison of currents at two extreme locations of a protected zone. These currents will differ in magnitude, phase or both during fault occurrence [1].